// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2015 Benoit Steiner <benoit.steiner.goog@gmail.com>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_CXX11_TENSOR_TENSOR_UINT128_H
#define EIGEN_CXX11_TENSOR_TENSOR_UINT128_H

namespace Eigen {
namespace internal {

    template <uint64_t n> struct static_val
    {
        static const uint64_t value = n;
        EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE operator uint64_t() const { return n; }

        EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE static_val() {}

        template <typename T> EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE static_val(const T& v)
        {
            EIGEN_UNUSED_VARIABLE(v);
            eigen_assert(v == n);
        }
    };

    template <typename HIGH = uint64_t, typename LOW = uint64_t> struct TensorUInt128
    {
        HIGH high;
        LOW low;

        template <typename OTHER_HIGH, typename OTHER_LOW>
        EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE TensorUInt128(const TensorUInt128<OTHER_HIGH, OTHER_LOW>& other) : high(other.high), low(other.low)
        {
            EIGEN_STATIC_ASSERT(sizeof(OTHER_HIGH) <= sizeof(HIGH), YOU_MADE_A_PROGRAMMING_MISTAKE);
            EIGEN_STATIC_ASSERT(sizeof(OTHER_LOW) <= sizeof(LOW), YOU_MADE_A_PROGRAMMING_MISTAKE);
        }

        template <typename OTHER_HIGH, typename OTHER_LOW>
        EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE TensorUInt128& operator=(const TensorUInt128<OTHER_HIGH, OTHER_LOW>& other)
        {
            EIGEN_STATIC_ASSERT(sizeof(OTHER_HIGH) <= sizeof(HIGH), YOU_MADE_A_PROGRAMMING_MISTAKE);
            EIGEN_STATIC_ASSERT(sizeof(OTHER_LOW) <= sizeof(LOW), YOU_MADE_A_PROGRAMMING_MISTAKE);
            high = other.high;
            low = other.low;
            return *this;
        }

        template <typename T> EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE explicit TensorUInt128(const T& x) : high(0), low(x)
        {
            eigen_assert((static_cast<typename conditional<sizeof(T) == 8, uint64_t, uint32_t>::type>(x) <= NumTraits<uint64_t>::highest()));
            eigen_assert(x >= 0);
        }

        EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE TensorUInt128(HIGH y, LOW x) : high(y), low(x) {}

        EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE operator LOW() const { return low; }
        EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE LOW lower() const { return low; }
        EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE HIGH upper() const { return high; }
    };

    template <typename HL, typename LL, typename HR, typename LR>
    EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool operator==(const TensorUInt128<HL, LL>& lhs, const TensorUInt128<HR, LR>& rhs)
    {
        return (lhs.high == rhs.high) & (lhs.low == rhs.low);
    }

    template <typename HL, typename LL, typename HR, typename LR>
    EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool operator!=(const TensorUInt128<HL, LL>& lhs, const TensorUInt128<HR, LR>& rhs)
    {
        return (lhs.high != rhs.high) | (lhs.low != rhs.low);
    }

    template <typename HL, typename LL, typename HR, typename LR>
    EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool operator>=(const TensorUInt128<HL, LL>& lhs, const TensorUInt128<HR, LR>& rhs)
    {
        if (lhs.high != rhs.high)
        {
            return lhs.high > rhs.high;
        }
        return lhs.low >= rhs.low;
    }

    template <typename HL, typename LL, typename HR, typename LR>
    EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE bool operator<(const TensorUInt128<HL, LL>& lhs, const TensorUInt128<HR, LR>& rhs)
    {
        if (lhs.high != rhs.high)
        {
            return lhs.high < rhs.high;
        }
        return lhs.low < rhs.low;
    }

    template <typename HL, typename LL, typename HR, typename LR>
    EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE TensorUInt128<uint64_t, uint64_t> operator+(const TensorUInt128<HL, LL>& lhs, const TensorUInt128<HR, LR>& rhs)
    {
        TensorUInt128<uint64_t, uint64_t> result(lhs.high + rhs.high, lhs.low + rhs.low);
        if (result.low < rhs.low)
        {
            result.high += 1;
        }
        return result;
    }

    template <typename HL, typename LL, typename HR, typename LR>
    EIGEN_DEVICE_FUNC EIGEN_ALWAYS_INLINE TensorUInt128<uint64_t, uint64_t> operator-(const TensorUInt128<HL, LL>& lhs, const TensorUInt128<HR, LR>& rhs)
    {
        TensorUInt128<uint64_t, uint64_t> result(lhs.high - rhs.high, lhs.low - rhs.low);
        if (result.low > lhs.low)
        {
            result.high -= 1;
        }
        return result;
    }

    template <typename HL, typename LL, typename HR, typename LR>
    static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE TensorUInt128<uint64_t, uint64_t> operator*(const TensorUInt128<HL, LL>& lhs, const TensorUInt128<HR, LR>& rhs)
    {
        // Split each 128-bit integer into 4 32-bit integers, and then do the
        // multiplications by hand as follow:
        //   lhs      a  b  c  d
        //   rhs      e  f  g  h
        //           -----------
        //           ah bh ch dh
        //           bg cg dg
        //           cf df
        //           de
        // The result is stored in 2 64bit integers, high and low.

        const uint64_t LOW = 0x00000000FFFFFFFFLL;
        const uint64_t HIGH = 0xFFFFFFFF00000000LL;

        uint64_t d = lhs.low & LOW;
        uint64_t c = (lhs.low & HIGH) >> 32LL;
        uint64_t b = lhs.high & LOW;
        uint64_t a = (lhs.high & HIGH) >> 32LL;

        uint64_t h = rhs.low & LOW;
        uint64_t g = (rhs.low & HIGH) >> 32LL;
        uint64_t f = rhs.high & LOW;
        uint64_t e = (rhs.high & HIGH) >> 32LL;

        // Compute the low 32 bits of low
        uint64_t acc = d * h;
        uint64_t low = acc & LOW;
        //  Compute the high 32 bits of low. Add a carry every time we wrap around
        acc >>= 32LL;
        uint64_t carry = 0;
        uint64_t acc2 = acc + c * h;
        if (acc2 < acc)
        {
            carry++;
        }
        acc = acc2 + d * g;
        if (acc < acc2)
        {
            carry++;
        }
        low |= (acc << 32LL);

        // Carry forward the high bits of acc to initiate the computation of the
        // low 32 bits of high
        acc2 = (acc >> 32LL) | (carry << 32LL);
        carry = 0;

        acc = acc2 + b * h;
        if (acc < acc2)
        {
            carry++;
        }
        acc2 = acc + c * g;
        if (acc2 < acc)
        {
            carry++;
        }
        acc = acc2 + d * f;
        if (acc < acc2)
        {
            carry++;
        }
        uint64_t high = acc & LOW;

        // Start to compute the high 32 bits of high.
        acc2 = (acc >> 32LL) | (carry << 32LL);

        acc = acc2 + a * h;
        acc2 = acc + b * g;
        acc = acc2 + c * f;
        acc2 = acc + d * e;
        high |= (acc2 << 32LL);

        return TensorUInt128<uint64_t, uint64_t>(high, low);
    }

    template <typename HL, typename LL, typename HR, typename LR>
    static EIGEN_DEVICE_FUNC EIGEN_STRONG_INLINE TensorUInt128<uint64_t, uint64_t> operator/(const TensorUInt128<HL, LL>& lhs, const TensorUInt128<HR, LR>& rhs)
    {
        if (rhs == TensorUInt128<static_val<0>, static_val<1>>(1))
        {
            return TensorUInt128<uint64_t, uint64_t>(lhs.high, lhs.low);
        }
        else if (lhs < rhs)
        {
            return TensorUInt128<uint64_t, uint64_t>(0);
        }
        else
        {
            // calculate the biggest power of 2 times rhs that's less than or equal to lhs
            TensorUInt128<uint64_t, uint64_t> power2(1);
            TensorUInt128<uint64_t, uint64_t> d(rhs);
            TensorUInt128<uint64_t, uint64_t> tmp(lhs - d);
            while (lhs >= d)
            {
                tmp = tmp - d;
                d = d + d;
                power2 = power2 + power2;
            }

            tmp = TensorUInt128<uint64_t, uint64_t>(lhs.high, lhs.low);
            TensorUInt128<uint64_t, uint64_t> result(0);
            while (power2 != TensorUInt128<static_val<0>, static_val<0>>(0))
            {
                if (tmp >= d)
                {
                    tmp = tmp - d;
                    result = result + power2;
                }
                // Shift right
                power2 = TensorUInt128<uint64_t, uint64_t>(power2.high >> 1, (power2.low >> 1) | (power2.high << 63));
                d = TensorUInt128<uint64_t, uint64_t>(d.high >> 1, (d.low >> 1) | (d.high << 63));
            }

            return result;
        }
    }

}  // namespace internal
}  // namespace Eigen

#endif  // EIGEN_CXX11_TENSOR_TENSOR_UINT128_H
